Том 64, № 3 (2024)

We found an additional Canestrini’s organ in some males of Cobitis lutheri, C. derzhavini, and Misgurnus chipisaniensis, which normally have one lamina circularis on the first branched ray of the pectoral fin. We consider this as a manifestation of atavism. In the case of C. lutheri and C. derzhavini, this phenomenon mimics the state observed in the Bibarba lineage, and in the case of the pond loach, in the Bicanestrinia lineage. It is suggested that the primitive ancestral state for the entire Northern Clade of loaches should be considered to be the presence of two or even three laminae circularis in the pectoral fin of sexually mature males. In most lineages this state is lost, however, there probably was a phylogenetic reversion in the ancestor of the Bicanestrinia group through fixation of the atavistic state as a norm.

The results of a study of the distribution of eggs of Baikal omul Coregonus migratorius in a large foothill watercourse in Siberia in 1935–2022 are presented. The distanse of omul spawning migration in the Selenga River (some of the river parameters are taken into account since 1920) depends on a certain combination of abiotic environmental factors, biological parameters of spawners, timing of entry into the river, and the number of their spawning herd. The distance of migration has a high inverse correlation with the degree of maturity of the spawners, which is expressed by the maturity index of omul females, as well as with the timing of herd entry into the river and water consumption at the beginning of migration (September). The higher the maturity of the reproductive products of spawners, the shorter the migration route, and vice versa. In addition, the maturity of spawners also determines the timing (date) of stock entry into the river: less mature individuals enter the river earlier and are distributed at spawning grounds higher upstream, while more mature individuals enter the river later and spawn downstream of the river. The distance of omul spawning migration increases during a decrease in the water flow of the Selenga River in September and, on the contrary, decreases with increase in water flow. Finally, The distance of the spawning route of omul in Selenga is determined by the size of the spawning stock: the higher the number of spawners, the more area they need for spawning and the longer their spawning route. Water temperature does not influence the length of omul spawning migration. The spawning run takes place against the background of a decrease in water temperature in the river.

Charrs of the genus Salvelinus (Salmonidae) exhibit diverse patterns of heterochrony throughout their ontogeny, resulting in contrasting intraspecific phenotypic variation. This study focuses on isolated populations of Dolly Varden charr, Salvelinus malma, inhabiting cold-water lakes within the subnival belt on the Kamchatka Peninsula. Our study reveals a previously undescribed trend towards paedomorphosis in these populations. Specialization is associated with inhibition of somatic growth compared to the widely distributed migratory (anadromous and river-lake) Dolly Varden from open water systems. Juvenile charrs from landlocked lakes differ in relatively high muscle fat content. Rates of sexual maturation and morphological differentiation remain similar to those of migratory populations. Paedomorphic trends in skull structure are insignificant and the numbers of meristic serial elements do not decrease. Charrs from landlocked mountain lakes grow to a maximum length of 20 cm reaching an age of eight to nine years, while the median age of spawners is 6.2 years. Migratory charrs have the same lifespan, but spawners are 1.6–2.0 times larger. Dwarfism tends to evolve over a small number of generations, as similar phenotypes have been described in populations from the lakes originated more than 12,000 and 400 years ago.

From 1982–1990 to 2006–2010 in the western part of the Bering Sea biomass of the walleye pollock Gadus chalcogrammus decreased by almost an order of magnitude, from 7.2 to 0.7 million tons. However, in the last decade (2011–2020) its biomass increased to the long-term average value (4.0 million tons). In the eastern part of the sea, the pollock biomass dynamics was of the wave-like nature with the highest value in 1982–1990 and the lowest, in 2006–2010. The food spectrum of the walleye pollock is wide and includes 16 taxonomic groups of aquatic organisms. The main part of average annual food mass consumed by pollock in the Bering Sea in 1982–2020 consisted of zooplankton (74.1%). During different study periods, annual feed consumption varied from 91.1 to 373.0 (average 239.3) million tons per year. Significant fluctuations in the volume of food consumed are mainly associated with the dynamics of the species’ biomass.

Numerous studies show that species identification of representatives of the genus Alosa using various genetic markers is often difficult and the search for more specific biomarkers is required. For the first time we analyzed polymorphism of COI gene fragment of mitochondrial DNA of two representatives of this genus (A. tanaica and A. kessleri), supplemented with new data on A. immaculata, from the waters of the Ponto-Caspian basin in comparative aspect with other representatives of the herring (Clupeoidea) genera Alosa, Clupea, Clupeonella, Sprattus, and Sardinops. The main result was the conclusion that within the genus Alosa, it is not possible to identify species using the marker used. On the one hand, specimens collected from morphologically distinct individuals and identified as different species have the same haplotypes. On the other hand, samples belonging to different species differ from each other by an insignificant number of nucleotide substitutions and do not form independent clades on the phylogram and haplotype network. This indicates the absence of genetic differentiation between the studied samples of herrings of genus Alosa into separate species and species groups when using DNA barcoding based on the COI gene. The reasons for such a phenomenon may be the following: 1) incorrect identification of species in catches, since shads (Alosidae) have high morphological flexibility and in many species, the main external morphological characters often overlap; 2) recent time of speciation by the standards of biological evolution for shads of genus Alosa; 3) difference in proportion of interspecific hybrids, which can vary significantly between populations of the same species.